To assess the effects of pindolol, a combined 5-HT1a antagonist and beta adrenoceptor antagonist (beta blocker), and of betaxolol, a pure beta blocker, on sleep. To provide normative data regarding the dose-response relationship of pindolol on sleep, to provide a tool for further investigation of the role of the 5-HT1a receptor in sleep regulation, and to disentangle the anti-serotonergic and anti-adrenergic properties of the potential effects of pindolol on sleep.